prmsgc.c

Netscape NSPR库源码

}

static void NotifyFinalizer(void)
{
    if (!PR_CLIST_IS_EMPTY(&_pr_finalQueue)) {
    PR_ASSERT( GC_IS_LOCKED() );
    PR_Notify(_pr_gcData.lock);
    }
}

void _PR_CreateFinalizer(PRThreadScope scope)
{
    if (!_pr_gcData.finalizer) {
    _pr_gcData.finalizer = PR_CreateThreadGCAble(PR_SYSTEM_THREAD,
                                        FinalizerLoop, 0,
                                        PR_PRIORITY_LOW, scope,
                                        PR_UNJOINABLE_THREAD, 0);
    
    if (_pr_gcData.finalizer == NULL)
        /* We are doomed if we can't start the finalizer */
        PR_Abort();

    }
}

void pr_FinalizeOnExit(void)
{
#ifdef DEBUG_warren
    OutputDebugString("### Doing finalize-on-exit pass\n");
#endif
    PR_ForceFinalize();
#ifdef DEBUG_warren
    OutputDebugString("### Finalize-on-exit complete. Dumping object left to memory.out\n");
    PR_DumpMemorySummary();
    PR_DumpMemory(PR_TRUE);
#endif
}

PR_IMPLEMENT(void) PR_ForceFinalize()
{
    LOCK_GC();
    NotifyFinalizer();
    while (!PR_CLIST_IS_EMPTY(&_pr_finalQueue)) {
    PR_ASSERT( GC_IS_LOCKED() );
    (void) PR_Wait(_pr_gcData.lock, PR_INTERVAL_NO_TIMEOUT);
    }
    UNLOCK_GC();

    /* XXX I don't know how to make it wait (yet) */
}

/************************************************************************/

typedef struct GCWeakStr {
    PRCList links;
    PRWord *object;
} GCWeak;

/*
** Find pointer to GCWeak struct from the list linkaged embedded in it
*/
#define WeakPtr(_qp) \
    ((GCWeak*) ((char*) (_qp) - offsetof(GCWeak,links)))

PRCList _pr_weakLinks = PR_INIT_STATIC_CLIST(&_pr_weakLinks);
PRCList _pr_freeWeakLinks = PR_INIT_STATIC_CLIST(&_pr_freeWeakLinks);

#define WEAK_FREELIST_ISEMPTY() (_pr_freeWeakLinks.next == &_pr_freeWeakLinks)

/*
 * Keep objects referred to by weak free list alive until they can be
 * freed
 */
static void PR_CALLBACK ScanWeakFreeList(void *notused) {
#ifdef XP_MAC
#pragma unused (notused)
#endif
    PRCList *qp = _pr_freeWeakLinks.next;
    while (qp != &_pr_freeWeakLinks) {
    GCWeak *wp = WeakPtr(qp);
    qp = qp->next;
    ProcessRootPointer(wp->object);
    }
}

/*
 * Empty the list of weak objects. Note that we can't call malloc/free
 * under the cover of the GC's lock (we might deadlock), so transfer the
 * list of free objects to a local list under the cover of the lock, then
 * release the lock and free up the memory.
 */
static void EmptyWeakFreeList(void) {
    if (!WEAK_FREELIST_ISEMPTY()) {
    PRCList *qp, freeLinks;

    PR_INIT_CLIST(&freeLinks);

    /*
     * Transfer list of free weak links from the global list to a
     * local list.
     */
    LOCK_GC();
    qp = _pr_freeWeakLinks.next;
    while (qp != &_pr_freeWeakLinks) {
        GCWeak *wp = WeakPtr(qp);
        qp = qp->next;
        PR_REMOVE_LINK(&wp->links);
        PR_APPEND_LINK(&wp->links, &freeLinks);
    }
    UNLOCK_GC();

    /* Free up storage now */
    qp = freeLinks.next;
    while (qp != &freeLinks) {
        GCWeak *wp = WeakPtr(qp);
        qp = qp->next;
        PR_DELETE(wp);
    }
    }
}

/*
 * Allocate a new weak node in the weak objects list
 */
static GCWeak *AllocWeakNode(void)
{
    EmptyWeakFreeList();
    return PR_NEWZAP(GCWeak);
}

static void FreeWeakNode(GCWeak *node)
{
    PR_DELETE(node);
}

/*
 * Check the weak links for validity. Note that the list of weak links is
 * itself weak (otherwise we would keep the objects with weak links in
 * them alive forever). As we scan the list check the weak link object
 * itself and if it's not marked then remove it from the weak link list
 */
static void CheckWeakLinks(void) {
    PRCList *qp;
    GCWeak *wp;
    PRWord *p, h, tix, **weakPtrAddress;
    CollectorType *ct;
    PRUint32 offset;

    qp = _pr_weakLinks.next;
    while (qp != &_pr_weakLinks) {
    wp = WeakPtr(qp);
    qp = qp->next;
    if ((p = wp->object) != 0) {
        h = p[0];        /* Grab header word */
        if ((h & MARK_BIT) == 0) {
        /*
         * The object that has a weak link is no longer being
         * referenced; remove it from the chain and let it get
         * swept away by the GC. Transfer it to the list of
         * free weak links for later freeing.
         */
        PR_REMOVE_LINK(&wp->links);
        PR_APPEND_LINK(&wp->links, &_pr_freeWeakLinks);
        collectorCleanupNeeded = 1;
        continue;
        }
        
	    /* Examine a live object that contains weak links */
        tix = GET_TYPEIX(h);
        ct = &_pr_collectorTypes[tix];
        PR_ASSERT((ct->flags != 0) && (ct->gctype.getWeakLinkOffset != 0));
        if (0 == ct->gctype.getWeakLinkOffset) {
        /* Heap is probably corrupted */
        continue;
        }

        /* Get offset into the object of where the weak pointer is */
        offset = (*ct->gctype.getWeakLinkOffset)(p + 1);

        /* Check the weak pointer */
        weakPtrAddress = (PRWord**)((char*)(p + 1) + offset);
        p = *weakPtrAddress;
        if (p != 0) {
        h = p[-1];    /* Grab header word for pointed to object */
        if (h & MARK_BIT) {
            /* Object can't be dead */
            continue;
        }
        /* Break weak link to an object that is about to be swept */
        *weakPtrAddress = 0;
        }
    }
    }
}

/************************************************************************/

/*
** Perform a complete garbage collection
*/

extern GCLockHook *_pr_GCLockHook;

static void dogc(void)
{
    RootFinder *rf;
    GCLockHook* lhook;

    GCScanQ scanQ;
    GCSeg *sp, *esp;
    PRInt64 start, end, diff;

#if defined(GCMETER) || defined(GCTIMINGHOOK)
    start = PR_Now();
#endif

    /*
    ** Stop all of the other threads. This also promises to capture the
    ** register state of each and every thread
    */

    /* 
    ** Get all the locks that will be need during GC after SuspendAll. We 
    ** cannot make any locking/library calls after SuspendAll.
    */
    if (_pr_GCLockHook) {
        for (lhook = _pr_GCLockHook->next; lhook != _pr_GCLockHook; 
          lhook = lhook->next) {
          (*lhook->func)(PR_GCBEGIN, lhook->arg);
        }
    }

    PR_SuspendAll();

#ifdef GCMETER
    /* Reset meter info */
    if (_pr_gcMeter & _GC_METER_STATS) {
        fprintf(stderr,
                "[GCSTATS: busy:%ld skipped:%ld, alloced:%ld+wasted:%ld+free:%ld = total:%ld]\n",
                (long) _pr_gcData.busyMemory,
                (long) meter.skippedFreeChunks,
                (long) meter.allocBytes,
                (long) meter.wastedBytes,
                (long) _pr_gcData.freeMemory,
                (long) _pr_gcData.allocMemory);
    }        
    memset(&meter, 0, sizeof(meter));
#endif

    PR_LOG(_pr_msgc_lm, PR_LOG_ALWAYS, ("begin mark phase; busy=%d free=%d total=%d",
                     _pr_gcData.busyMemory, _pr_gcData.freeMemory,
                     _pr_gcData.allocMemory));

    if (_pr_beginGCHook) {
    (*_pr_beginGCHook)(_pr_beginGCHookArg);
    }

    /*
    ** Initialize scanQ to all zero's so that root finder doesn't walk
    ** over it...
    */
    memset(&scanQ, 0, sizeof(scanQ));
    pScanQ = &scanQ;

    /******************************************/
    /* MARK PHASE */

    EmptyFreelists();

    /* Find root's */
    PR_LOG(_pr_msgc_lm, PR_LOG_WARNING,
           ("begin mark phase; busy=%d free=%d total=%d",
        _pr_gcData.busyMemory, _pr_gcData.freeMemory,
            _pr_gcData.allocMemory));
    METER(_pr_scanDepth = 0);
    rf = _pr_rootFinders;
    while (rf) {
    _GCTRACE(GC_ROOTS, ("finding roots in %s", rf->name));
    (*rf->func)(rf->arg);
    rf = rf->next;
    }
    _GCTRACE(GC_ROOTS, ("done finding roots"));

    /* Scan remaining object's that need scanning */
    ScanScanQ(&scanQ);
    PR_ASSERT(pScanQ == &scanQ);
    PR_ASSERT(scanQ.queued == 0);
    METER({
    if (_pr_scanDepth > _pr_maxScanDepth) {
        _pr_maxScanDepth = _pr_scanDepth;
    }
    });

    /******************************************/
    /* FINALIZATION PHASE */

    METER(_pr_scanDepth = 0);
    PrepareFinalize();

    /* Scan any resurrected objects found during finalization */
    ScanScanQ(&scanQ);
    PR_ASSERT(pScanQ == &scanQ);
    PR_ASSERT(scanQ.queued == 0);
    METER({
    if (_pr_scanDepth > _pr_maxScanDepth) {
        _pr_maxScanDepth = _pr_scanDepth;
    }
    });
    pScanQ = 0;

    /******************************************/
    /* SWEEP PHASE */

    /*
    ** Sweep each segment clean. While we are at it, figure out which
    ** segment has the most free space and make that the current segment.
    */
    CheckWeakLinks();
    _GCTRACE(GC_SWEEP, ("begin sweep phase"));
    _pr_gcData.freeMemory = 0;
    _pr_gcData.busyMemory = 0;
    sp = segs;
    esp = sp + nsegs;
    while (sp < esp) {
        if (SweepSegment(sp)) {
            /*
            ** Segment is now free and has been replaced with a different
            ** segment object.
            */
            esp--;
            continue;
        }
        sp++;
    }

#if defined(GCMETER) || defined(GCTIMINGHOOK)
    end = PR_Now();
#endif
#ifdef GCMETER
    LL_SUB(diff, end, start);
    PR_LOG(GC, PR_LOG_ALWAYS,
	   ("done; busy=%d free=%d chunks=%d total=%d time=%lldms",
	    _pr_gcData.busyMemory, _pr_gcData.freeMemory,
	    meter.numFreeChunks, _pr_gcData.allocMemory, diff));
    if (_pr_gcMeter & _GC_METER_FREE_LIST) {
        PRIntn bin;
        fprintf(stderr, "Freelist bins:\n");
        for (bin = 0; bin < NUM_BINS; bin++) {
            GCFreeChunk *cp = bins[bin];
            while (cp != NULL) {
                fprintf(stderr, "%3d: %p %8ld\n",
                        bin, cp, (long) cp->chunkSize);
                cp = cp->next;
            }
        }
    }
#endif

    if (_pr_endGCHook) {
    (*_pr_endGCHook)(_pr_endGCHookArg);
    }

    /* clear the running total of the bytes allocated via BigAlloc() */
    bigAllocBytes = 0;

    /* And resume multi-threading */
    PR_ResumeAll();

    if (_pr_GCLockHook) {
        for (lhook = _pr_GCLockHook->prev; lhook != _pr_GCLockHook; 
          lhook = lhook->prev) {
          (*lhook->func)(PR_GCEND, lhook->arg);
        }
    }

    /* Kick finalizer */
    NotifyFinalizer();
#ifdef GCTIMINGHOOK
    if (_pr_gcData.gcTimingHook) {
	PRInt32 time;
	LL_SUB(diff, end, start);
	LL_L2I(time, diff);
	_pr_gcData.gcTimingHook(time);
    }
#endif
}

PR_IMPLEMENT(void) PR_GC(void)
{
    LOCK_GC();
    dogc();
    UNLOCK_GC();

    EmptyWeakFreeList();
}

/*******************************************************************************
 * Heap Walker
 ******************************************************************************/

/*
** This is yet another disgusting copy of the body of ProcessRootPointer
** (the other being ProcessRootBlock), but we're not leveraging a single
** function in their cases in interest of performance (avoiding the function
** call).
*/
static PRInt32 PR_CALLBACK
pr_ConservativeWalkPointer(void* ptr, PRWalkFun walkRootPointer, void* data)
{
  PRWord *p0, *p, *segBase;
  GCSeg* sp;

  p0 = (PRWord*) ptr;

  /*
  ** XXX:  
  ** Until Win16 maintains lowSeg and highSeg correctly,
  ** (ie. lowSeg=MIN(all segs) and highSeg = MAX(all segs))
  ** Allways scan through the segment list
  */
#if !defined(WIN16)
  if (p0 < _pr_gcData.lowSeg) return 0;                  /* below gc heap */
  if (p0 >= _pr_gcData.highSeg) return 0;                /* above gc heap */
#endif

  /* NOTE: inline expansion of InHeap */
  /* Find segment */
  sp = lastInHeap;
  if (!sp || !IN_SEGMENT(sp,p0)) {
    GCSeg *esp;
    sp = segs;
    esp = segs + nsegs;
    for (; sp < esp; sp++) {
      if (IN_SEGMENT(sp, p0)) {
	lastInHeap = sp;
	goto find_object;
      }
    }
    return 0;
  }

  find_object:
    /* NOTE: Inline expansion of FindObject */
    /* Align p to it's proper boundary before we start fiddling with it */
    p = (PRWord*) ((PRWord)p0 & ~(BYTES_PER_WORD-1L));
    segBase = (PRWord *) sp->base;
    do {
        if (IS_HBIT(sp, p)) {
            goto winner;
        }
        p--;
    } while (p >= segBase);

    /*
    ** We have a pointer into the heap, but it has no header
    ** bit. This means that somehow the very first object in the heap
    ** doesn't have a header. This is impossible so when debugging
    ** lets abort.
    */
#ifdef DEBUG
    PR_Abort();
#endif
    return 0;

 winner:
    return walkRootPointer(p, data);
}

static PRInt32 PR_CALLBACK
pr_ConservativeWalkBlock(void **base, PRInt32 count,
			 PRWalkFun walkRootPointer, void* data)
{
    PRWord *p0;
    while (--count >= 0) {
	PRInt32 status;
        p0 = (PRWord*) *base++;
	status = pr_ConservativeWalkPointer(p0, walkRootPointer, data);
	if (status) return status;
    }
    return 0;
}